1. Field of the Invention
The present invention relates to a shape memory alloy actuator.
2. Description of the Related Art
A shape memory alloy changes its shape with phase transformation caused by a change in the temperature. Actuators that utilize deformation of such a shape memory alloy have characteristics that are advantageous in reducing the size and weight of the actuators.
For example, Japanese Patent Application Laid-Open No. 57-141704 teaches to change the shape of a shape memory alloy by supplying an electrical current to it and to measures its resistance that changes with the change in the shape thereby controlling contraction and expansion of the shape memory alloy. Thus, this document discloses a technology in which the actuator itself functions also as a sensor.
In an actuator that uses a shape memory alloy wire, it is desirable that resistance feed back control be performed by measuring the resistance of the shape memory alloy thereby controlling the position of a moving body, as is the case with the above described prior art.